Curable silicone composition for the production of composite soft magnetic materials, and composite soft magnetic materials

ABSTRACT

A curable silicone composition for the production of composite soft magnetic materials comprising at least (A) a curable organopolysiloxane, (B) a curing agent, (C) a soft magnetic powder, and (D) an organosiloxane represented by the general formula: {R 1   a R 2   (3−a) SiO(R 2   2 SiO) n } b SiR 2 {4−(b+c)}(OR 3 ) c  wherein R 1  is a monovalent hydrocarbon group having at lease one aliphatic unsaturated bond, R 2  is the same as R 1  or a different monovalent hydrocarbon group having no aliphatic unsaturated bonds, R 3  is an alkyl group or an alkoxyalkyl group, the subscript &lt;&lt;a&gt;&gt; is an integer from 1 to 3, the subscript &lt;&lt;b&gt;&gt; is an integer from 1 to 3, the subscript &lt;&lt;c&gt;&gt; is an integer from 1 to 3, the subscript &lt;&lt;b+c&gt;&gt; is an integer from 2 to 4 and the subscript &lt;&lt;n&gt;&gt; is an integer of 0 or greater), as well as composite soft magnetic materials obtained by curing said composition. The invention provides a curable silicone composition capable of producing the above-mentioned composite soft magnetic materials despite containing a large amount of a soft magnetic powder used to obtain composite soft magnetic materials of superior electromagnetic wave absorption characteristics, as well as composite soft magnetic materials of superior electromagnetic wave absorption characteristics and of superior flame retardancy and thermal conductivity.

The present invention relates to a curable silicone composition for theproduction of composite soft magnetic materials and to composite softmagnetic materials. More specifically, it relates to a curable siliconecomposition capable of producing the above-mentioned composite softmagnetic materials despite containing a large amount of a soft magneticpowder used to obtain composite soft magnetic materials of superiorelectromagnetic wave absorption characteristics, as well as to compositesoft magnetic materials of superior electromagnetic wave absorptioncharacteristics and of superior flame retardancy and thermalconductivity.

In addition, in the present invention, the term “electromagnetic waveabsorption characteristics” refers to a broad range of characteristicsincluding not only far electromagnetic field absorption, but also nearelectromagnetic field absorption.

BACKGROUND OF THE INVENTION

Curable silicone compositions containing soft magnetic powders, as wellas composite soft magnetic materials obtained by curing them, arepublicly known, for instance, from Japanese Laid Open (Unexamined orKokai) Patent Application No. 2000-294977, Japanese Laid Open(Unexamined or Kokai) Patent Application No. 2001-44687, Japanese LaidOpen (Unexamined or Kokai) Patent Application No. 2001-294752, andJapanese Laid Open (Unexamined or Kokai) Patent Application No.2001-11918. Generally speaking, curable silicone compositions with highloadings of soft magnetic powder are necessary for the improvement ofthe electromagnetic wave absorption characteristics of composite softmagnetic materials.

However, the problem is that homogeneous compositions are not obtained,or the moldability of the resultant compositions deteriorates whencurable silicone compositions are highly loaded with soft magneticpowders.

The present inventors arrived at the present invention as a result ofin-depth investigations into the above-mentioned problems.

Namely, it is an object of the present invention to provide a curablesilicone composition capable of producing the above-mentioned compositesoft magnetic materials despite containing a large amount of softmagnetic powder used to obtain composite soft magnetic materials ofsuperior electromagnetic wave absorption characteristics, as well ascomposite soft magnetic materials of superior electromagnetic waveabsorption characteristics and of superior flame retardancy and thermalconductivity.

THE INVENTION

The inventive curable silicone composition for the production ofcomposite soft magnetic materials is characterized by comprising atleast (A) a curable organopolysiloxane, (B) a curing agent, (C) a softmagnetic powder, and (D) an organosiloxane represented by the generalformula:{R¹ _(a)R² _((3−a))SiO(R² ₂SiO)_(n}b)SiR² _((4−(b+c)))(OR³)_(c)(where R¹ is a monovalent hydrocarbon group having an aliphaticunsaturated bond or bonds, R² are similar or different monovalenthydrocarbon groups having no aliphatic unsaturated bonds, R³ is an alkylgroup or an alkoxyalkyl group, the subscript <<a>> is an integer from 1to 3, the subscript <<b>> is an integer from 1 to 3, the subscript <<c>>is an integer from 1 to 3, the subscript <<b+c>> is an integer from 2 to4, and the subscript <<n>> is an integer of 0 or greater).

In addition, the composite soft magnetic materials of the presentinvention are characterized in that they are obtained by curing theabove-described composition.

DETAILED DESCRIPTION OF THE INVENTION

First of all, detailed explanations will be provided regarding theinventive curable silicone composition for the production of compositesoft magnetic materials.

Component (A), the main ingredient of the present composition, is acurable organopolysiloxane, and component (B) is a curing agent used forcross-linking the above-mentioned component (A). There are nolimitations concerning the consistency of cured products obtained bycuring the present composition, which may be, for instance,high-hardness rubber-like, low-hardness rubber-like, or gel-like. Inaddition, there are no limitations concerning the cure mechanism of thepresent composition. Hydrosilation reactions, organic peroxide-basedfree radical reactions, and condensation reactions are suggested asexamples thereof, with hydrosilation reactions being preferable becausethe composition can be cured fast by heating while generating noby-products.

When the present composition is cured by a hydrosilation reaction,component (A) is preferably an organopolysiloxane having an average ofat least 0.1 silicon-bonded alkenyl groups per molecule, morepreferably, an organopolysiloxane having an average of at least 0.5silicon-bonded alkenyl groups per molecule, and especially preferably,an organopolysiloxane having an average of at least 0.8 silicon-bondedalkenyl groups per molecule. This is due to the fact that the resultantcomposition tends to fail to completely cure if the average number ofsilicon-bonded alkenyl groups per molecule is below the lower limit ofthe above-mentioned ranges.

Some examples of the alkenyl groups in the organopolysiloxane include,for instance, vinyl, allyl, butenyl, pentenyl, and hexenyl, with vinylbeing preferable. In addition, examples of silicon-bonded groups otherthan the alkenyl groups in the organopolysiloxane include, for instance,methyl, ethyl, propyl, butyl, pentyl, hexyl, and other alkyl groups;cyclopentyl, cyclohexyl, and other cycloalkyl groups; phenyl, tolyl,xylyl, and other aryl groups; benzyl, phenetyl, and other aralkylgroups; 3,3,3-trifluoropropyl, 3-chloropropyl, and other halogenatedalkyl groups, with alkyl and aryl groups being preferable, and methyland phenyl being especially preferable. In addition, while there are nolimitations concerning the viscosity of the organopolysiloxane at 25°C., it is preferably in the range of from 50 to 100.000 mPa.s and,especially preferably, in the range of from 100 to 50,000 mPa.s. This isdue to fact that the physical characteristics of the resultant siliconecured product tend to noticeably decrease when its viscosity at 25° C.is below the lower limit of the above-mentioned ranges and, on the otherhand, to the fact that the handleability of the resultant curablesilicone composition tends to conspicuously deteriorate when it exceedsthe upper limit of the above-mentioned ranges. There are no limitationsconcerning the molecular structure of such an organopolysiloxane, whichmay be, for instance, linear, branched, partially branched linear, ordendritic (dendrimer-like), and is preferably linear or partiallybranched linear. In addition, the organopolysiloxane may be ahomopolymer having one of the above-mentioned molecular structures, acopolymer comprising these molecular structures, or a mixture of suchpolymers.

Examples of such organopolysiloxanes include, for instance,dimethylpolysiloxane having both ends of the molecular chain blocked bydimethylvinylsiloxy groups, dimethylpolysiloxane having both ends of themolecular chain blocked by methylphenylvinylsiloxy groups, copolymer ofmethylphenylsiloxane and dimethylsiloxane having both ends of themolecular chain blocked by dimethylvinylsiloxy groups, copolymer ofmethylvinylsiloxane and dimethylsiloxane having both ends of themolecular chain blocked by dimethylvinylsiloxy groups, copolymermethylvinylsiloxane and dimethylsiloxane having both ends of themolecular chain blocked by trimethylsiloxy groups,methyl(3,3,3-trifluoropropyl)polysiloxane having both ends of themolecular chain blocked by dimethylvinylsiloxy groups, copolymer ofmethylvinylsiloxane and dimethylsiloxane having both ends of themolecular chain blocked by silanol groups, copolymer ofmethylphenylsiloxane, methylvinylsiloxane, and dimethylsiloxane havingboth ends of the molecular chain blocked by silanol groups, andorganosiloxane copolymer consisting of siloxane units represented by theformula (CH₃)₃SiO_(1/2), siloxane units represented by the formula(CH₃)₂(CH₂═CH)SiO_(1/2), siloxane units represented by the formulaCH₃SiO_(3/2), and siloxane units represented by the formula(CH₃)₂SiO_(2/2).

When the present composition is cured by a hydrosilation reaction,component (B) comprises a platinum catalyst and an organopolysiloxanehaving an average of at least two silicon-bonded hydrogen atoms permolecule.

Examples of silicon-bonded groups other than the hydrogen atoms in theorganopolysiloxane include, for instance, methyl, ethyl, propyl, butyl,pentyl, hexyl, and other alkyl groups; cyclopentyl, cyclohexyl, andother cycloalkyl groups; phenyl, tolyl, xyiyi, and other aryl groups,benzyl, phenetyl, and other aralkyl groups; 3,3,3-trifluoropropyl,3-chloropropyl, and other halogenated alkyl groups, with alkyl and arylgroups being preferable, and methyl and phenyl being especiallypreferable. In addition, while there are no limitations concerning theviscosity of the organopolysiloxane at 25° C., it is preferably in therange of from 1 to 100,000 mPa.s and, especially preferably, in therange of from 1 to 5,000 mPa.s. There are no limitations concerning themolecular structure of such an organopolysiloxane, which may be, forinstance, linear, branched, partially branched linear, or dendritic(dendrimer-like). The organopolysiloxane may be a homopolymer having oneof the above-mentioned molecular structures, a copolymer comprisingthese molecular structures, or a mixture of such polymers.

Examples of such organopolysiloxanes include, for instance,dimethylpolysiloxane having both ends of the molecular chain blocked bydimethylhydrogensiloxy groups, copolymer of methylhydrogensiloxane anddimethylsiloxane having both ends of the molecular chain blocked bytrimethylsiloxy groups, copolymer of methylhydrogensiloxane anddimethylsiloxane having both ends of the molecular chain blocked bydimethylhydrogensiloxy groups, and organosiloxane copolymer consistingof siloxane units represented by the formula (CH₃)₃SiO_(1/2), siloxaneunits represented by the formula (CH₃)₂HSiO_(1/2), and siloxane unitsrepresented by the formula SiO_(4/2).

In the present composition, the content of the organopolysiloxane issuch that the quantity of silicon-bonded hydrogen atoms in thiscomponent per 1 mol of the silicon-bonded alkenyl groups in component(A) is preferably in the range of from 0.1 to 10 mol and, especiallypreferably, in the range of from 0.1 to 5 mol. This is due to the factthat the resultant curable silicone composition tends to fail tocompletely cure if the content of the component is below the lower limitof the above-mentioned ranges, and, on the other hand, to the fact thatthe resultant silicone cured product becomes extremely rigid andnumerous cracks appear on its surface when the content exceeds the upperlimit of the above-mentioned ranges.

In addition, the platinum catalyst is exemplified by chloroplatinicacid, alcohol solutions of chloroplatinic acid, olefin complexes ofplatinum, alkenylsiloxane complexes of platinum, and carbonyl complexesof platinum. The content of the platinum catalyst is preferably suchthat the quantity of platinum metal in the catalyst relative tocomponent (A), in terms of weight units, is in the range of from 0.01 to1,000 ppm, and, especially curable silicone composition tends to fail tocompletely cure when the content of the component is below the lowerlimit of the above-mentioned ranges, and, on the other hand, to the factthat the rate of cure of the resultant curable silicone composition doesnot considerably increase even if it exceeds the upper limits of theabove-mentioned ranges.

In addition, when the present composition is cured by a free radicalreaction, there are no particular limitations concerning theorganopolysiloxane of component (A), but it is preferably anorganopolysiloxane having at least one silicon bonded alkenyl group permolecule.

The alkenyl groups of the organopolysiloxane are exemplified by the samealkenyl groups as those mentioned above and are preferably representedby vinyl. In addition, in this organopolysiloxane, silicon bonded groupsother than the alkenyl groups are exemplified by the same alkyl,cycloalkyl, aryl, aralkyl, and halogenated alkyl groups as thosementioned above and are preferably represented by alkyl and aryl groups,with methyl and phenyl being especially preferable. In addition,although there are no limitations concerning the viscosity of theorganopolysiloxane at 25° C., the viscosity is preferably in the rangeof from 50 to 100,000 mPa.s and, especially preferably, in the range offrom 100 to 50,000 mPa.s. This is due to fact that the physicalcharacteristics of the resultant silicone cured product tend tonoticeably decrease when its viscosity at 25° C. is below the lowerlimit of the above-mentioned ranges and, on the other hand, to the factthat the handleability of the resultant curable silicone compositiontends to conspicuously deteriorate when it exceeds the upper limit ofthe above-mentioned ranges. There are no limitations concerning themolecular structure of such an organopolysiloxane, which may be, forinstance, linear, branched, partially branched linear, or dendritic(dendrimer-like), and is preferably linear or partially branched linear.In addition, the organopolysiloxane may be a homopolymer having one ofthe above-mentioned molecular structures, a copolymer comprising thesemolecular structures, or a mixture of such polymers.

Examples of such organopolysiloxanes include, for instance,dimethylpolysiloxane having both ends of the molecular chain blocked bydimethylvinylsiloxy groups, dimethylpolysiloxane having both ends of themolecular chain blocked by methylphenylvinylsiloxy groups, copolymer ofmethylphenylsiloxane and dimethylsiloxane having both ends of themolecular chain blocked by dimethylvinylsiloxy groups, copolymer ofmethylvinylsiloxane and dimethylsiloxane having both ends of themolecular chain blocked by dimethylvinylsiloxy groups, copolymermethylvinylsiloxane and dimethylsiloxane having both ends of themolecular chain blocked by trimethylsiloxy groups,methyl(3,3,3-trifluoropropyl)polysiloxane having both ends of themolecular chain blocked by dimethylvinylsiloxy groups, copolymer ofmethylvinylsiloxane and dimethylsiloxane having both ends of themolecular chain blocked by silanol groups, copolymer ofmethylphenylsiloxane, methylvinylsiloxane, and dimethylsiloxane havingboth ends of the molecular chain blocked by silanol groups, andorganosiloxane copolymer consisting of siloxane units represented by theformula (CH₃)₃SiO_(1/2), siloxane units represented by the formula(CH₃)₂(CH₂═CCH)SiO_(1/2), siloxane units represented by the formulaCH₃SiO_(3/2), and siloxane units represented by the formula(CH₃)₂SiO_(2/2).

In addition, when the present composition is cured by a free radicalreaction, component (B) is an organic peroxide. The organic peroxidesare exemplified by benzoyl peroxide, p-methylbenzoyl peroxide, dicumylperoxide, 2,5-dimethyl-bis(2,5-t-butylperoxy)hexane, di-t-butylperoxide, and t-butyl perbenzoate. The content of the organic peroxideis preferably in the range of from 0.1 to 5 parts by weight per 100parts by weight of component (A).

In addition, when the present composition is cured by a condensationreaction, component (A) is an organopolysiloxane having at least twosilanol groups or silicon-bonded hydrolyzable groups per molecule.Examples of the silicon-bonded hydrolyzable groups of theorganopolysiloxane include, for instance, methoxy, ethoxy, propoxy, andother alkoxy groups; vinyloxy, isopropenyloxy, 1-ethyl-2-methylvinyloxy,and other alkenoxy groups; methoxyethoxy, ethoxyethoxy, methoxypropoxy,and other alkoxyalkoxy groups; acetoxy, octanoyloxy, and other acyloxygroups; dimethyl ketoxime, methyl ethyl ketoxime, and other ketoximegroups; dimethylamino, diethylamino, dibutylamino, and other aminogroups; dimethylaminoxy, diethylaminoxy, and other aminoxy groups; andN-methylacetamido, N-ethylacetamido, and other amido groups. Inaddition, in this organopolysiloxane, silicon-bonded groups other thanthe silanol groups or silicon-bonded hydrolyzable groups are exemplifiedby the same alkyl, cycloalkyl, alkenyl, aryl, aralkyl, and halogenatedalkyl groups as those mentioned above. Also, while there are nolimitations concerning the viscosity of the organopolysiloxane at 25°C., it is preferably in the range of from 20 to 100,000 mPa.s and,especially preferably, in the range of from 100 to 100,000 mPa.s.Additionally, organosiloxanes of component (D) are not included in thiscomponent.

Examples of such organopolysiloxanes include, for instance,dimethylpolysiloxane having both ends of the molecular chain blocked bysilanol groups, copolymer of methylphenylsiloxane and dimethylsiloxanehaving both ends of the molecular chain blocked by silanol groups,dimethylpolysiloxane having both ends of the molecular chain blocked bytrimethoxysiloxy groups, copolymer of methylphenylsiloxane anddimethylsiloxane having both ends of the molecular chain blocked bytrimethoxysiloxy groups, dimethylpolysiloxane having both ends of themolecular chain blocked by methyldiimethoxysiloxy groups,dimethylpolysiloxane having both ends of the molecular chain blocked bytriethoxysiloxy groups, and dimethylpolysiloxane having both ends of themolecular chain blocked by trimethoxysilylethyl groups.

In addition, when the present composition is cured by a condensationreaction, component (B) is a silane having at least three silicon-bondedhydrolyzable groups per molecule or a partial hydrolyzate thereof, and,if necessary, a condensation reaction catalyst.

The silicon-bonded hydrolyzable groups of the silane are exemplified bythe same alkoxy, alkoxyalkoxy, acyloxy, ketoxime, alkenoxy, amino,aminoxy, and amido groups as those mentioned above. In addition, in thesilane, silicon bonded groups other than the hydrolyzable groups areexemplified by the same alkyl, cycloalkyl, alkenyl, aryl, aralkyl, andhalogenated alkyl groups as those mentioned above. Examples of suchsilanes and their partial hydrolizates include, for instance,methyltriethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, andethyl orthosilicate.

In the present coinmposition, the content of the silane or its partialhydrolyzate is preferably in the range of from 0.01 to 20 parts byweight, and, especially preferably, in the range of from 0.1 to 10 partsby weight per 100 parts by weight of component (A). This is due to thefact that the storage stability and adhesive property of the resultantcomposition decreases when the content of the silane or its partialhydrolyzate is below the lower limit of the above-mentioned ranges, and,on the other hand, the cure of the resultant composition noticeablyslows down when it exceeds the upper limit of the above-mentionedranges.

Also, the condensation reaction catalyst is an optional component and isnot essential, for instance, when a silane having aminoxy, amino, andketoxime groups is used as the curing agent. Examples of suchcondensation reaction catalysts include, for instance, tetrabutyltitanate, tetraisopropyl titanate, and other organotitanates;diisopropoxy bis(acetyl acetato)titanium, diisopropoxy bis(ethylacetacetato)titanium, and other organotitanium chelate compounds;aluminum tris(acetyl acetonate), aluminum tris(ethyl acetoacetate), andother organic aluminum compounds; zirconium tetra(acetyl acetonate),zirconium tetrabutylate, and other organic zirconium compounds;dibutyltin dioctoate, dibutyltin dilaurate, dibutyltin-2-ethylhexoate,and other organotin compounds; tin naphthenate, tin oleate, tinbutyrate, cobalt naphthenate, zinc stearate, and other metal salts oforganic carboxylic acids; hexylamine, dodecylamine phosphate, and otheramine compounds and their salts; benzyltriethylammonium acetate andother quaternary aminonium salts; potassium acetate, lithium nitrate,and other of lower fatty acid salts of alkali metals;dimethylhydroxylamine, diethylhydroxylamine, and otherdialkylhydroxylamines; and, in addition, organosilicon compoundscontaining guanidyl groups.

There are no limitations concerning the content of the condensationreaction catalyst, but preferably, the content is in the range of from0.01 to 20 parts by weight, and, especially preferably, in the range offrom 0.1 to 10 parts by weight per 100 parts by weight of component (A).This is due to the fact that, when this catalyst is essential, theresultant composition tends to fail to completely cure if the content isbelow the lower limit of the above-mentioned ranges, and, on the otherhand, the storage stability of the resultant composition tends todecrease when it exceeds the upper limit of the above-mentioned ranges.

Component (C) is a soft magnetic powder used to impart electromagneticwave absorption characteristics to composite soft magnetic materialsformed by curing the present composition. Examples of such powdersinclude, for instance, soft magnetic metal powders or magnetic oxidepowders (ferrite powders). Such soft magnetic metal powders areexemplified by iron powder (carbonyl iron powder) or powders ofiron-based alloys such as Fe—Si alloys, Fe—Al alloys, Fe—Si—Al alloys,Fe—Si—Cr alloys, Fe—Ni alloys, Fe—Ni—Co alloys, Fe—Ni—Mo alloys, Fe—Coalloys, Fe—Si—Al—Cr alloys, Fe—Si—B alloys, Fe—Si—Co—B alloys, etc. Inaddition, such ferrite powders are exemplified by Mn—Zn ferrites,Mn—Mg—Zn ferrites, Mg—Cu—Zn ferrites, Ni—Zn ferrites, Ni—Cu—Zn ferrites,Cu—Zn ferrites, and other spinel ferrites, and W-type, Y-type, Z-type,M-type and other hexagonal ferrites. Because ferrite powders arenoncombustible, from the standpoint of flame retardancy, they are moreefficient than metal magnetic powders. Furthermore, because ferritesgenerally have higher electrical resistance than metallic magneticmaterials, they are more suitable when insulating properties arerequired. In addition, in terms of shape, they may be granular,spherical, or oblate. Among the above-mentioned shapes, using oblatesoft magnetic powders is preferable when modern electromagnetic noisefrequencies are taken into consideration. This is due to the fact thatimparting an oblate shape to a soft magnetic powder suppresses thediamagnetic field acting on the soft magnetic powder and, as a result,magnetic resonance phenomena can be produced at frequencies of I GHz orless, which are currently at the center of the noise problem. If D₅₀ isthe mean particle size obtained when the value of 50% is reached in theprocess of summing up weight starting from small particle sizes, asdetermined using a particle size meter, then the size of the softmagnetic powder is preferably such that the value of D₅₀ is in the rangeof from 1 to 50 μm and, even more preferably, in the range of from 3 to30 μm. In addition, when the shape of the soft magnetic powder isoblate, the aspect ratio is preferably in the range of from 5 to 100,and, especially preferably, in the range of from 10 to 50. Among suchsoft magnetic powders, it is preferable to use oblate soft magneticpowders. This is due to the fact that with soft magnetic metal powders,it is relatively easy to impart an oblate shape to the material, and, asa result, it is possible to achieve high electromagnetic wave absorptionperformance at frequencies of 1 GHz or less, which are currently at thecore of the noise problem, as mentioned above. Also, oblate softmagnetic metal powders have a high specific surface areas and highactivity and, as a result, from the standpoint of the safety of thecomposite soft magnetic material fabrication process as well as theflame retardancy of the composite soft magnetic materials, it ispreferable for the surface of such powders to be subjected to oxidizingtreatment. In addition, with such soft magnetic powders, a single typeor, depending on the intended use, several types of powder can be usedtogether. Component (C) can be prepared in accordance with thepreparation processes described in Japanese Patent Publication No. Sho54-27557 and Japanese Patent Publication No. 2,523,388.

There are no limitations concerning the content of component (C),however, in order to form composite soft magnetic materials possessingexcellent electromagnetic wave absorption characteristics, it ispreferable for the content to be in the range of from 40 to 1,000 partsby weight per 100 parts by weight of component (A). In order to formcomposite soft magnetic materials of particularly superiorelectromagnetic wave absorption characteristics, the content ofcomponent (C) should be preferably in the range of from 50 to 1,000parts by weight, more preferably, in the range of from 100 to 1,000parts by weight, and, especially preferably, in the range of from 200 to1,000 parts by weight per 100 parts by weight of component (A). On theother hand, in order to obtain a curable silicone composition for theproduction of composite soft magnetic materials of superior moldability,the content of component (C) should be preferably in the range of from40 to 900 parts by weight, and especially preferably, in the range offrom 40 to 800 parts by weight per 100 parts by weight of component (A).With account taken of the above, the content of component (C) should bepreferably in the range of from 50 to 900 parts by weight, even morepreferably, in the range of from 100 to 900 parts by weight, andespecially preferably, in the range of from 200 to 800 parts by weightper 100 parts by weight of component (A). This is due to the fact thatthe magnetic characteristics of the resultant composite soft magneticmaterial tend to be insufficient when the content of component (C) isbelow the lower limit of the above-mentioned ranges and, on the otherhand, uniformly dispersing component (C) in the resultant component (A)tends to become impossible and molding becomes difficult when it exceedsthe upper limit of the above-mentioned ranges.

Component (D), which is represented by the general formula:{R¹ _(a)R² _((3−a)SiO(R) ² ₂SiO)_(n)}SiR²{4−(b+c)}(OR³)_(c)is an organosiloxane used to prevent deterioration in the moldability ofthe resultant composition even when the present composition is highlyloaded with component (C). R¹ in the formula above is a monovalenthydrocarbon group having aliphatic unsaturated bonds. Examples of suchgroups include, for instance, vinyl, allyl, butenyl, hexenyl, decenyl,undecenyl, dodecenyl, tridecenyl, tetradecenyl, pentadecenyl,hexadecenyl, heptadecenyl, octadecenyl, nonadecenyl, eicosenyl, andother linear alkenyl groups; isopropenyl, 2-methyl-2-propenyl,2-methyl-10-undecenyl, and other branched alkenyl groups;vinylcyclohexyl, vinylcyclododecyl, and other cyclic alkyl groups havingaliphatic unsaturated bonds; vinylphenyl and other aryl groups withaliphatic unsaturated bonds; vinylbenzyl, vinylphenetyl, and otheraralkyl groups with aliphatic unsaturated bonds. Preferably, however,such groups are represented by linear alkenyl groups and, especiallypreferably, by vinyl, allyl, and hexenyl. While there are no limitationsconcerning the position of the aliphatic unsaturated bonds in R¹,preferably, it is located away from bonded silicon atoms. Also, R² inthe formula above are similar or different monovalent hydrocarbon groupshaving no aliphatic unsaturated bonds, examples of which include, forinstance, methyl, ethyl, propyl, butyl, hexyl, decyl, and other linearalkyl groups; isopropyl, teri-butyl, isobutyl, and other branched alkylgroups; cyclohexyl and other cyclic alkyl groups; phenyl, tolyl, xylyl,and other aryl groups; benzyl, phenetyl, and other aralkyl groups, withalkyl and aryl groups being preferable, alkyl groups having from 1 to 4carbon atoms being even more preferable, and methyl and ethyl beingespecially preferable. In addition, R³ is an alkyl or alkoxyalkyl group,examples of which include, for instance, methyl, ethyl, propyl, butyl,hexyl, decyl, and other linear alkyl groups; isopropyl, tert-butyl,isobutyl, and other branched alkyl groups; cycloalkyl and other cyclicalkyl groups; methoxyethyl, ethoxyethyl, methoxypropyl, and otheralkoxyalkyl groups. Preferably, such groups are represented by alkylgroups, and especially preferably, by methyl, ethyl, and propyl. Inaddition, the subscript <<a>> in the formula above is an integer of from1 to 3, preferably, 1. Also, the subscript <<b>> in the formula above isan integer from 1 to 3, preferably, 1. Also, the subscript <<c>> in theformula above is an integer from 1 to 3, preferably, 3. Here, thesubscript <<b+c>> in the formula above is an integer from 2 to 4. Inaddition, the subscript <<n>> in the formula above is an integer of 0 orgreater, preferably, an integer from 0 to 100, more preferably, aninteger from 1 to 100, still more preferably, an integer from 5 to 100,even more preferably, an integer from 10 to 100, and especiallypreferably, an integer from 10 to 75.

Processes used for the preparation of such a component (D) include, forinstance, a process using a dealcoholation condensation reaction betweenan organosiloxane having one end of the molecular chain blocked by asilanol group, represented by the general formula:R¹ _(a)R² _((3−a))SiO(R² ₂SiO)_(n)H,and an alkoxysilane compound having at least two silicon-bonded alkoxygroups per molecule in the presence of an acid catalyst such as aceticacid.

In such a silanol-capped organosiloxane, R¹ in the formula above is amonovalent hydrocarbon group having aliphatic unsaturated bonds,exemplified by the same groups as those mentioned above. In addition, R²in the formula are similar or different monovalent hydrocarbon groupshaving no aliphatic unsaturated bonds, exemplified by the same groups asthose mentioned above. Also, the subscript <<a>> in the formula above isan integer from 1 to 3, preferably, 1. In addition, the subscript <<n>>in the formula above is an integer of 0 or greater, preferably, aninteger from 0 to 100, more preferably, an integer from 1 to 100, stillmore preferably, an integer from 5 to 100, even more preferably, aninteger from 10 to 100, and especially preferably, an integer from 10 to75.

Also, the alkoxysilane compounds having at least two silicon-bondedalkoxy groups per molecule are represented by the general formula:R² _((4−d))Si(OR³)_(d)In this alkoxysilane compound, R² in the formula above is a monovalenthydrocarbon group having no aliphatic unsaturated bonds, exemplified bythe same groups as those mentioned above. Also, R³ is an alkyl oralkoxyalkyl group, exemplified by the same groups as those mentionedabove. In addition, the subscript <<d>> in the formula above is aninteger from 2 to 4, preferably, 4.

Examples of such alkoxysilane compounds include, for instance,dimethoxydimethylsilane, dimethoxydiethylsilane, diethoxydimethylsilane,diethoxydiethylsilane, and other dialkoxydialkylsilane compounds;trimethoxymethylsilane, trimethoxyethylsilane, trimethoxypropylsilane,triethoxyrnethylsilane, triethoxyethylsilane, and othertrialkoxyalkylsilane compounds; tetrainethoxysilane, tetraethoxysilane,tetrapropoxysilane, and other tetraalkoxysilane coinmpounds. Inaddition, examples of the acid catalysts include, for instance, aceticacid, propionic acid, and other fatty acids.

Component (D) is exemplified by the following compounds.(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₅Si(OCH₃)₃(CH₂═CHCH₂)(CH₃)₂SiO{(CH₃)₂SiO}₅Si(OCH₃)₃(CH_(s)—CHCH₂CH₂CH₂CH₂)(CH₃)₂SiO{(CH₃)₂SiO}₅Si(OCH₃)₃(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₇Si(OCH₃)₃(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₇Si(OC₂H₅)₃(CH₂═CHCH₂)(CH₃)₂SiO{(CH₃)₂SiO}₇Si(OCH₃)₃(CH₂═CHCH₂CH₂C H₂CH₂)(CH₃)₂SiO{(CH₃)₂SiO}₇Si(OCH₃)₃(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₇SiCH₃(OCH₃)₂(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₇SiCH₃(OCH₃)₂(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}]₂₅Si(OCH₃)₃(CH₂═CHCH₂)(CH₃)₂SiO{(CH₃)₂SiO}₂₅Si(OCH₃)₃(CH₂═CHCH₂CH₂CH₂CH₂)(CH₃)₂SiO {(CH₃)₂SiO}₂₅Si(OCH₃)₃(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₂₅Si(OC₂H₅)₃(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₂₅SiCH₃(OCH₃)₂(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₅₀Si(OCH₃)₃(CH₂═CHCH₂)(CH₃)₂SiO{(CH₃)₂SiO}₅₀Si(OCH₃)₃(CH₂═CHCH₂CH₂CH₂CH₂)(CH₃)₂SiO{(CH₃)₂SiO}₅₀Si(OCH₃)₃(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₅₀Si(OC₂H₅)₃(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₅₀SiCH₃(OCH₃)₂

There are no limitations concerning the content of component (D) so longas the quantity of the component makes it possible to treat of thesurface of component (C) to improve its dispersibility in the resultantcurable silicone composition for the production of composite softmagnetic materials. Preferably, it is in the range of from 0.05 to 10parts by weight, more preferably, in the range of from 0.1 to 10 partsby weight, and especially preferably, in the range of from 0.1 to 5parts by weight per 100 parts by weight of component (C). This is due tothe fact that when the content of component (D) is below the lower limitof the above-mentioned ranges, using a large amount of component (C)leads to a decrease in the moldability of the resultant curable siliconecomposition for the production of composite soft magnetic materials andcomponent (C) tends to easily precipitate and separate when theresultant composite soft magnetic materials are kept in storage, and, onthe other hand, to the fact that the physical strength of the resultantcomposite soft magnetic materials tends to deteriorate when the contentexceeds the upper limit of the above-mentioned ranges.

Examples of methods used to treat the surface of component (C) withcomponent (D) include, for instance, mixing component (C) and component(D) to pretreat the surface of component (C) with component (D), ormixing component (A) and component (C) and then adding component (D) totreat the surface of component (C) in component (A) with component (D),with the latter method being preferable. In the thus obtainedcoinmposition, component (D) may be introduced as a result of treatingthe surface of component (C) or as a result of separately introducing itin the present composition.

So long as the purpose of the present invention is not impaired, otheroptional components, for instance, fillers such as fumed silica,precipitated silica, and fumed titanium oxide, as well as fillersobtained by making the surface of the above-mentioned fillershydrophobic by treating it with organosilicon compounds; and, inaddition, pigments, dyes, fluorescent dyes, heat-resistant additives,triazole compounds and other flame retardancy-imparting agents,plasticizers, and adhesion-imparting agents may be introduced into thepresent composition. In particular, when the present composition iscured by a hydrosilation reaction, to improve the handleability of thepresent composition, the composition preferably contains2-methyl-3-butyn-2-ol, 2-phenyl-3-butyn-2-ol, 1-ethynyl-1-cyclohexanol,and other acetylene compounds, 3-methyl-3-penten-1-yne,3,5-dimethyl-3-hexen-1-yne, and other ene-yne compounds, phosphinecompounds, mercaptan compounds, and other cure reaction inhibitors.Although there are no limitations concerning the content of the curereaction inhibitors, preferably, the content should be in the range offrom 0.001 to 1.0% by weight relative to the present composition.

Next, detailed explanations are provided regarding the composite softmagnetic materials of the present invention.

The composite soft magnetic materials of the present invention arecharacterized by the fact that they are obtained by curing theabove-mentioned composition. There are no limitations concerning themethods used to cure the above-mentioned composition, which may be, forinstance, molding the above-mentioned composition and then allowing itto stand at room temperature, molding the above-mentioned compositionand then heating it to 50-200° C., or using injection molding. Inaddition, there are no limitations concerning the consistency of thethus obtained composite soft magnetic materials, which may be, forinstance, high-hardness rubber-like, low-hardness rubber-like, orgel-like. In addition, there are no limitations concerning the shape ofthe composite soft magnetic materials, which may be, for instance,sheet-shaped, in addition to variously shaped articles molded using amold. Such sheet-shaped composite soft magnetic materials areexemplified by materials having peelable film adhered to both sidesthereof, or materials having film permanently integrated therewith onone side and peelable film adhered thereto on the other side.

Methods used to fabricate sheet-shaped composite soft magnetic materialsare exemplified by a process, in which the above-mentioned compositionis sandwiched between sheets of film that can be peeled from the curedproduct of the above-mentioned composition, and, in this state,subjected to pressure to produce the desired thickness and cured byheating. The heating can be carried out simultaneously with pressureapplication or in an oven after removing from the press.

In addition, methods used to fabricate sheet-shaped composite softmagnetic materials with film integrated therewith on one side areexemplified by a process, in which the above-mentioned composition issandwiched between a sheet of film that can be peeled from the curedproduct of the above-mentioned composition and a sheet of easilyadhesive film whose surface, if necessary, can be primed with silanecoupling agents, titanium coupling agents, aluminum coupling agents,etc. or treated with plasma, corona discharge, or alkali in advance,and, in this state, subjected to pressure to produce the desiredthickness and cured by heating.

EXAMPLES

The curable silicone composition for the production of composite softmagnetic materials and composite soft magnetic materials of the presentinvention are explained in detail below by referring to applicationexamples and comparative examples. In addition, characteristics reportedin the application examples are values measured at 25° C. Also, in theapplication examples, the organosiloxane oligomer represented by theformula:(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₂₅Si(OCH₃)₃was prepared via a methanol-eliminating condensation reaction carriedout by combining an organosiloxane oligomer represented by the formula:(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₂₅OHwith tetramethoxysilane (in the amount of 10 mol per 1 mol of theabove-mentioned organosiloxane oligomer) and heating the mixture in thepresence of an acetic acid catalyst.

In addition, the moldability of the curable silicone composition for theproduction of composite soft magnetic materials was evaluated in thefollowing manner. Moldability of curable silicone composition for theproduction of composite soft magnetic materials

After sandwiching the curable silicone composition for the production ofcomposite soft magnetic materials between sheets of ethylenetetrafluoride resin film with a thickness of 0.2 mm and making thecomposition into a layer with a thickness of 2 mm, the above-mentionedcomposition was cured by heating at 120° C. for 60 minutes.Subsequently, the ethylene tetrafluoride resin film was peeled off, andevaluation was carried out to determine whether a sheet-shaped compositesoft magnetic material had been obtained, designating the results of theevaluation as ◯, i.e. excellent moldability, when it was possible tomold a uniform composite soft magnetic material, and x, i.e. poormoldability, when it proved impossible to mold a uniform composite softmagnetic material.

In addition, the electromagnetic wave absorption characteristics, flameretardancy, and the thermal conductivity of the composite soft magneticmaterials were measured in the following manner.

Electromagnetic Wave Absorption Characteristics of Composite SoftMagnetic materials

After sandwiching the curable silicone composition for the production ofcomposite soft magnetic materials between sheets of polypropylene resinfilm with a thickness of 0.2 mm and making the composition into a layerwith a thickness of 0.5 mm, the above-mentioned composition was cured byheating at 120° C. for 60 minutes, whereupon the polypropylene resinfilm was peeled off, producing a sheet of composite soft magneticmaterial. The magnetic permeability of the composite soft magneticmaterial was measured at a frequency of 10 MHz using the RFImpedance/material Analyzer 4291 B from Agilent Technologies. Also,since the electromagnetic wave absorption performance of soft magneticmaterials is based on energy absorption due to magnetic resonancephenomena and the magnetic resonance-induced energy absorption increaseswith the magnetic permeability of the materials, here, theelectromagnetic wave absorption characteristics were evaluated bymeasuring the magnetic permeability of the materials.

Flame Retardancy of Composite Soft Magnetic Materials

After sandwiching the curable silicone composition for the production ofcomposite soft magnetic materials between sheets of ethylenetetrafluoride resin film with a thickness of 0.2 mm and making thecomposition into a layer with a thickness of 0.5 mm, the above-mentionedcomposition was cured by heating at 120° C. for 60 minutes.Subsequently, the ethylene tetrafluoride resin film was peeled off,producing a sheet of composite soft magnetic material, whose flameretardancy was evaluated using the UL 94 20-mm Vertical Burning Test.

Thermal Conductivity of Composite Soft Magnetic Materials

After molding the curable silicone composition for the production ofcomposite soft magnetic materials into a sheet with a thickness of 15mm, the above-mentioned composition was cured by heating at 120° C. for60 minutes. The thermal conductivity of the resultant composite softmagnetic material was measured using the Quick Thermal ConductivityMeter QTM-500 from Kyoto Electronics Manufacturing Co., Ltd. inaccordance with the hot-wire method specified in JIS R2616.

Application Example 1

9.87 parts by weight of dimethylpolysiloxane with a viscosity of 400mPa.s (vinyl group content=0.44% by weight) having both ends of themolecular chain blocked by dimethylvinylsiloxy groups, 20.58 parts byweight of dimethylpolysiloxane with a viscosity of 35,000 mPa.s (vinylgroup content=0.09% by weight) having both ends of the molecular chainblocked by dimethylvinylsiloxy groups, 67.5 parts by weight of Fe—Si—Cralloy powder with a D₅₀ (particle size obtained when the value of 50% isreached in the process of summing up weight starting from small particlesizes, as determined using a particle size meter) of 15 μm and aspecific surface area of 1.4 m²/g, which was prepared in accordance withthe method described in Japanese Patent Publication No. 2,523,388 andsubjected to pulverizing treatment to impart it with an oblate shape andoxidizing treatment to create an oxide film on its surface, and 1.0parts by weight of organosiloxane oligomer represented by the formula:(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₂₅Si(OCH₃)₃were mixed in a mixer, thereby treating the surface of theabove-mentioned alloy powder with said organosiloxane oligomer.

Next, 0.9 parts by weight of copolymer of methylhydrogensiloxane anddimethylsiloxane having both ends of the molecular chain blocked bytrimethylsiloxy groups (silicon-bonded hydrogen atom content=0.74% byweight), which had a viscosity of 5 mPa.s and an average of fivesilicon-bonded hydrogen atoms per molecule, and, as a cure reactioninhibitor, 0.05 parts by weight of 1-ethynyl-1-cyclohexanol werecombined therewith.

Finally, a silicone rubber composition for the production of compositesoft magnetic materials was prepared by combining the above-mentionedmixture with 0.1 parts by weight of complex of platinum and1,3-divinyl-1,1,3,3-tetramethyldisiloxane with a platinum content of0.5% by weight. The moldability of the silicone rubber composition forthe production of composite soft magnetic materials and thecharacteristics of the sheet-shaped composite soft magnetic materialobtained by curing it are listed in Table 1.

Application Example 2

19.92 parts by weight of dimethylpolysiloxane with a viscosity of 10,000mPa.s (vinyl group content=0.12% by weight) having both ends of themolecular chain blocked by dimethylvinylsiloxy groups, 77.5 parts byweight of Fe—Si—Cr alloy powder with a D₅₀ (particle size obtained whenthe value of 50% is reached in the process of summing up weight startingfrom small particle sizes, as determined using a particle size meter) of15 μm and a specific surface area of 0.4 m²/g, which was prepared inaccordance with the method described in Japanese Patent Publication No.2,523,388 and subjected to pulverizing treatment to impart it with anoblate shape and oxidizing treatment to create an oxide film on itssurface, and 1.0 parts by weight of organosiloxane oligomer representedby the formula:(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₂₅Si(OCH₃)₃were mixed in a mixer, thereby treating the surface of theabove-mentioned alloy powder with said organosiloxane oligomer.

Next, 1.43 parts by weight of copolymer of methylhydrogensiloxane anddimethylsiloxane having both ends of the molecular chain blocked bytrimethylsiloxy groups (silicon-bonded hydrogen atoin content=0.13% byweight), which had a viscosity of 20 mPa.s and an average of threesilicon-bonded hydrogen atoms per molecule, and, as a cure reactioninhibitor, 0.05 parts by weight of 1-ethynyl-1-cyclohexanol werecombined therewith.

Finally, a silicone rubber composition for the production of compositesoft magnetic materials was prepared by combining the above-mentionedmixture with 0.1 parts by weight of complex of platinum and1,3-divinyl-1,1,3,3-tetramethyldisiloxane with a platinum content of0.5% by weight. The moldability of the silicone rubber composition forthe production of composite soft magnetic materials and thecharacteristics of the sheet-shaped composite soft magnetic materialobtained by curing it are listed in Table 1.

Application Example 3

3.89 parts by weight of dimethylpolysiloxane with a viscosity of 400mPa.s (vinyl group content=0.44% by weight) having both ends of themolecular chain blocked by dimethylvinylsiloxy groups, 8.11 parts byweight of dimethylpolysiloxane with a viscosity of 35,000 mPa.s (vinylgroup content=0.09% by weight) having both ends of the molecular chainblocked by dimethylvinylsiloxy groups, 86.5 parts by weight of Mn—Mg—Znferrite powder with a D₅₀ (particle size obtained when the value of 50%is reached in the process of summing up weight starting from smallparticle sizes, as determined using a particle size meter) of 10 μm anda specific surface area of 0.5 m²/g, which was prepared in accordancewith the method described in Japanese Patent Publication No. Sho54-27557 and subjected to pulverizing treatment, and 1.0 parts by weightof organosiloxane oligomer represented by the formula:(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₂₅Si(OCH₃)₃with said organosiloxane oligomer.

Next, 0.35 parts by weight of copolymer of methylhydrogensiloxane anddimethylsiloxane having both ends of the molecular chain blocked bytrimethylsiloxy groups (silicon-bonded hydrogen atom content=0.74% byweight), which had a viscosity of 5 mPa.s and an average of fivesilicon-bonded hydrogen atoms per molecule, and, as a cure reactioninhibitor, 0.05 parts by weight of 1-ethynyl-1-cyclohexanol werecombined therewith.

Finally, a silicone rubber composition for the production of compositesoft magnetic materials was prepared by combining the above-mentionedmixture with 0.1 parts by weight of complex of platinum and1,3-divinyl-1,1,3,3-tetramethyidisiloxane with a platinum content of0.5% by weight. The moldability of the silicone rubber composition forthe production of composite soft magnetic materials and thecharacteristics of the sheet-shaped composite soft magnetic materialobtained by curing it are listed in Table 1.

Comparative Example 1

A silicone rubber composition for the production of composite softmagnetic materials was prepared in the same manner as in ApplicationExample 1, with the exception that the organosiloxane oligomerrepresented by the formula:(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₂₅Si(OCH₃)₃was not added as in Application Example 1. The moldability of thesilicone rubber composition for the production of composite softmagnetic materials and the characteristics of the sheet-shaped compositesoft magnetic material obtained by curing it are listed in Table 1.

Comparative Example 2

A silicone rubber composition for the production of composite softmagnetic materials was prepared in the same manner as in ApplicationExample 1, with the exception that an organosiloxane oligomerrepresented by the formula:(CH₃)₃SiO{(CH₃)₂SiO}₂₃Si(OCH₃)₃as added, in the same amount, instead of the organosiloxane oligomerrepresented by the formula:(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₂₅Si(OCH₃)₃The moldability of the silicone rubber composition for the production ofcomposite soft magnetic materials and the characteristics of thesheet-shaped composite soft magnetic material obtained by curing it arelisted in Table 1.

Comparative Example 3

A silicone rubber composition for the production of composite softmagnetic materials was prepared in the same manner as in ApplicationExample 3, with the exception that the organosiloxane oligomerrepresented by the formula:(CH₂═CH)(CH₃)₂SiO{(CH₃)₂SiO}₂₅Si(OCH₃)₃

was not added as in Application Example 3. The moldability of thesilicone rubber composition for the production of composite softmagnetic materials and the characteristics of the sheet-shaped compositesoft magnetic material obtained by curing it are listed in Table 1.TABLE 1 Example Present Invention Comparative Examples Parameter Appl.Ex. 1 Appl. Ex. 2 Appl. Ex. 3 Comp. Ex. 1 Comp. Ex. 2 Comp. Ex. 3Moldability ∘ ∘ ∘ x x x Voids present Voids present Sheet cannot beformed Magnetic 19 15 13 15 10 — permeability Flame CorrespondsCorresponds Corresponds Corresponds Corresponds — retardancy to V-1 toV-0 to V-0 to V-1 to V-1 Thermal 1.4 1.5 1.4 1.0 1.0 — conductivity(W/mK)

INDUSTRIAL APPLICABILITY

The inventive curable silicone composition for the production ofcomposite soft magnetic materials permits preparation of theabove-mentioned composite soft magnetic materials with excellentmoldability despite containing a large amount of a soft magnetic powderused to obtain a composite soft magnetic material of superiorelectromagnetic wave absorption characteristics. In addition, thecomposite soft magnetic materials of the present invention can provideelectromagnetic noise-canceling materials for electronic equipment ofsuperior electromagnetic wave absorption characteristics and superiorflame retardancy and thermal conductivity, and, furthermore, can provideelectromagnetic noise-canceling materials ensuring reduced environmentalload due to their flame retardancy even if halide material is notcontained.

1. A curable silicone composition for the production of composite softmagnetic materials, which comprises at least: (A) a curableorganopolysiloxane, (B) a curing agent, (C) a soft magnetic powder, and(D) an organosiloxane represented by the general formula:{R¹ _(a)R² _((3−a))SiO(R² ₂SiO)_(n)}_(b)SiR² _({4−(b+c)})(OR³)_(c)wherein R¹ is a monovalent hydrocarbon group having at least onealiphatic unsaturated bond, R² is the same as or a different monovalenthydrocarbon group having no aliphatic unsaturated bonds, R³ is an alkylgroup or an alkoxyalkyl group, the subscript <<a>> is an integer from 1to 3, the subscript <<b>> is an integer from 1 to 3, the subscript <<c>>is an integer from 1 to 3, the subscript <<b+c>> is an integer from 2 to4 and the subscript <<n>> is an integer of 0 or greater.
 2. Thecomposition of claim 1, wherein the curable silicone composition iscured by a hydrosilation reaction.
 3. The composition of claim 1,wherein component (C) is a soft magnetic metal powder or a magneticoxide powder (ferrite powder).
 4. The composition of claim 3, whereinthe soft magnetic metal powder is an oblate metal powder whose surfacehas been subjected to oxidizing treatment.
 5. The composition of claim1, wherein the content of component (C) is from 40 to 1,000 parts byweight per 100 parts by weight of component (A).
 6. The composition ofclaim 1, wherein the content of component (D) is from 0.05 to 10 partsby weight per 100 parts by weight of component (C).
 7. A composite softmagnetic material obtained by curing the curable silicone compositionaccording to claim
 1. 8. A composite soft magnetic material obtained bycuring the curable silicone composition according to claim
 2. 9. Acomposite soft magnetic material obtained by curing the curable siliconecomposition according to claim
 3. 10. A composite soft magnetic materialobtained by curing the curable silicone composition according to claim4.
 11. A composite soft magnetic material obtained by curing the curablesilicone composition according to claim
 5. 12. A composite soft magneticmaterial obtained by curing the curable silicone composition accordingto claim
 6. 13. The composite soft magnetic material of claim 7, whereinthe material is sheet-shaped.
 14. The composite soft magnetic materialof claim 8, wherein the material is sheet-shaped.
 15. The composite softmagnetic material of claim 9, wherein the material is sheet-shaped. 16.The composite soft magnetic material of claim 10, wherein the materialis sheet-shaped.
 17. The composite soft magnetic material of claim 11,wherein the material is sheet-shaped.
 18. The composite soft magneticmaterial of claim 12, wherein the material is sheet-shaped.